Within-group genetic relatedness affects survival and recruitment of group-living rodents

Background/Question/Methods

Kin selection predicts that genetic relatedness among group mates may improve survival of kin owing to reduced kin competition, and may enhance recruitment owing to cooperative breeding in group-living species.   However, few empirical studies have investigated demographic correlates of within-group genetic relatedness in social mammals.  We tested the predictions of kin selection using the Mongolian gerbil (Meriones unguiculatus) as a model species.  Mongolian gerbils are a social rodent, living in social groups year-round in the Mongolian Plateau.   We live trapped Mongolian gerbils biweekly in Inner Mongolia, China from May, 2006 through July, 2007 using capture-recapture methods.   We genotyped 358 captured gerbils using 9 microsatellite loci.  We evaluated effects of genetic relatedness and group size on survival and recruitment of Mongolian gerbils using the Cormack-Jolly-Seber (CJS) model and Jolly-Seber (JS) model within the program MARK.  Most approximating models for survival and recruitment were selected using the information-theoretic approach.   

Results/Conclusions

We determined optimal group size of 7.8 gerbils, at which survival peaked.  Genetic relatedness increased recruitment, but decreased survival.  Therefore, kinship of social group may enhance recruitment; however, detrimental effects of inbreeding between group mates may reduce survival of Mongolian gerbils.  Natural selection and kin selection may work in concert to shape population dynamics of group-living mammals.